OM617 Shimmy

[BHutch]

The car in question is an 85 300SD with about 99k. I've been trying to trouble shoot a slight shimmy or lope that happens at lower RPM's but I wonder if I'm chasing a white whale in that the 617 is not supposed to be the smoothest of engines.

The Problem:
At Idle it has an extremely subtle lope(air cleaner doesn't move but sound is prrrr-prrrr-prrrr instead of prrrrrrrrrrrrrrr) that becomes more pronounced as soon as any throttle is given(even the smallest amount). It has a period of about 1 cycle per second at 800 RPM's. It smooths out slightly up till 1300 or 1400 RPMs then has a pronounced lope of about 2 cycles per second. The travel from side to side is between 1/4 and 1/2". Above 1800 it seems to be smooth.

What I've done so far:
-Adjusted valves
-Popped and balanced injectors
-adjusted IP timing
-motor mounts are about a year old but I have reason to think Indy did not use MB mounts
-Motor shocks are a few months old
-Fuel hoses seem to be tight and filters are relatively fresh

I guess a compression test is in order but I use less than 1/2 qt. of oil per 3000 mi. and most of that is leaks. No abnormal smoking. My last oil analysis din't show high levels of fuel in the oil (or anything else for that matter). MPG seems to be average. Starts very well in the cold.

First, am I wasting my time tring to iron this out?
Second, if not, what are the possible culprits that I've missed?